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Randomly slow network until after DNS restart

Posted on 2013-10-25
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Last Modified: 2013-11-13
Dear experts,

I really hope you guys / girls can help us solve this terrible problem.

Problem:
The entire day the internal network is fast, an very stable. But for the past few weeks sometimes the network is randomly slow. All my 300 users are suddenly complaining that every thing is slow;

- Opening files
- Browsing the network
- Applications

We think this problem might be DNS related. But when we take a look at our DNS servers there is nothing wrong with them. No errors in the log files or anything. The problem goes away when we restart the DNS services on our DNS servers. Sometimes the problem stayes away for a week and sometimes for a couple of hours.

Server1:
OS: Windows server 2008 R2 all updates (virtual)
Roles: AD (Primary), DNS (AD Intergrated), DHCP
DNS forwarders are the DNS servers of my ISP and google's public DNS servers.

Server2:
OS: Windows server 2008 R2 all updates (virtual)
Roles: AD (secundary), DNS (AD Intergrated)
DNS forwarder is the Server1, witch i doubt is correct but i don't believe this is the cause of my problem.

This all has been a real brain teaser for me. Please help.
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Question by:mspren
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7 Comments
 
LVL 1

Expert Comment

by:miller3773
ID: 39600576
What is your DNS scavaging settings set to. If it is happening at almost regular intervals then your DNS servers could be removing old entries and having to rebuild it.
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Author Comment

by:mspren
ID: 39600619
DNS Scavaging is not enabled
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LVL 38

Expert Comment

by:Hypercat (Deb)
ID: 39600817
Remove all forwarders, both the one that refers Server2 to Server1, and the ones that forward from Server1 to external servers.  Make sure that the root hints are enabled so that you'll have external DNS resolution.  See if that helps.
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Author Comment

by:mspren
ID: 39600980
I'll give it a try, but doesnt this slow down the internet speed because the DNS server has to do all its work by himself?
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Accepted Solution

by:
Hypercat (Deb) earned 500 total points
ID: 39601006
Not really.  Your DNS server still has to query the upstream DNS server(s), and if there's a problem with one of them it could significantly slow things down. I've never had a significant slowdown or problem with the root servers, but I have experienced various problems over the years with using other forwarders.  There are, however, differing opinions about this, as with anything techno-based. Giving it a try doesn't hurt anything, though, and if it doesn't work well for you and/or fix your problem, you can always put the forwarders back.
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Author Comment

by:mspren
ID: 39604877
Ok, well i removed everything from the forwarders. I'll see how it goes. The randomly slow network sometimes stays out for a week.

I'll keep you updated.
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Author Closing Comment

by:mspren
ID: 39644684
perfect sollution
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